A mixture of H2 and NH3 has a volume of 153.2 cm3 0.00C and one atm. The mixture is cooled to the temperature of liquid nitrogen at which ammonia freezes out and the remaining gas is removed from the vessel. Upon warming the vessel to 0.00°C and one atm, the volume is 98.7 cm3. Calculate the mole fraction of NH3 in the original mixture.